A factory farm is a large-scale industrial operation that raises animals in high densities, prioritizing efficiency and output over traditional pasture-based methods. The U.S. Environmental Protection Agency uses the formal term “concentrated animal feeding operation,” or CAFO, and sets specific animal thresholds to classify them. A large CAFO confines at least 1,000 cattle, 2,500 pigs, 125,000 chickens, or 82,000 laying hens, among other categories. These operations now produce the vast majority of meat, eggs, and dairy sold in the United States.
How Factory Farms Are Officially Classified
The EPA divides CAFOs into three tiers based on the number of animals confined. Large CAFOs hit the thresholds listed above. Medium CAFOs fall below those numbers (for example, 300 to 999 cattle or 750 to 2,499 pigs) but qualify if they discharge manure or wastewater into nearby surface water. Small operations with fewer animals can also be designated as CAFOs on a case-by-case basis if regulators determine they’re significant polluters.
The defining feature isn’t just animal count. It’s confinement. Animals in a CAFO are kept in enclosed buildings or feedlots rather than grazing on open land. Feed is brought to them rather than grown on-site, which is why the UN Food and Agriculture Organization describes these systems as “landless.” The entire model is oriented toward rapid weight gain and maximum throughput.
What Life Looks Like for the Animals
Confinement spaces are tight. The industry standard for a battery cage, the wire enclosure used for egg-laying hens, provides roughly 67 square inches per bird. That’s smaller than a standard sheet of paper. Even with recent reforms in states like California, which raised the minimum to one square foot per hen, birds have limited room to move. Breeding pigs fare similarly: a conventional gestation crate gives a sow about 14 square feet, a space barely larger than her own body. California’s Proposition 12 pushed that minimum to 24 square feet, but gestation crates remain standard in most of the country.
Physical alterations are routine. Male beef calves are typically castrated before six months of age, often without anesthesia. Laying hens have the tips of their beaks trimmed to prevent pecking injuries caused by crowding. Piglets commonly have their tails docked for the same reason. Dairy calves are separated from their mothers shortly after birth. These practices are considered standard in the industry, though they’ve drawn increasing scrutiny from both animal welfare researchers and the public.
Environmental Footprint
The scale of waste is the central environmental issue. U.S. animal agriculture produces roughly 133 million tons of manure per year on a dry-weight basis, about 13 times more solid waste than the entire human population of the country generates. On a traditional farm, manure is spread across enough acreage to be absorbed as fertilizer. On a factory farm, it’s stored in open-air lagoons or sprayed onto nearby fields at rates the land often can’t handle.
When manure overwhelms the soil, nitrogen and phosphorus leach into groundwater and run off into rivers and streams. Groundwater near swine waste lagoons has been measured at 143 milligrams of nitrogen per liter. For context, algal blooms that choke aquatic life and create dead zones can be triggered by concentrations as low as 0.1 to 0.2 milligrams per liter. That’s a difference of roughly 700-fold. When waste lagoons spill or breach, the damage is immediate: researchers have documented severely depleted oxygen levels and extreme contamination stretching 30 kilometers downstream from a single spill point.
Despite federal regulations requiring discharge permits under the Clean Water Act, compliance is low. As of 2022, only 30 percent of CAFOs had obtained the required permits, a number that has actually declined from 33 percent in 2017.
Antibiotic Use and Disease Risk
An estimated 73 percent of all antibiotics sold worldwide are used in animals raised for food, not in human medicine. Much of this use isn’t for treating sick animals. Antibiotics are administered at low doses to promote faster growth and prevent infections that spread easily in crowded conditions. The problem is that this creates ideal conditions for bacteria to develop resistance. Drug-resistant strains of MRSA and E. coli have been found on both conventional and antibiotic-free swine farms, and resistant bacteria from food animals have been linked to infections in humans.
The crowding itself creates a separate category of risk. When thousands of genetically similar animals are packed into indoor facilities, viruses can circulate rapidly and mutate with each transmission. The intensification of poultry and pig farming has been directly tied to the emergence of H5N1 avian influenza and Nipah virus. Genetic homogeneity in livestock, meaning that most commercial animals share nearly identical immune systems, removes the natural firebreaks that would slow a pathogen’s spread in a more diverse population. Concentrated waste, long-distance animal transport, and high worker turnover all compound the risk.
Conditions for Workers
Slaughterhouse and processing plant jobs rank among the most physically demanding and dangerous in American industry. In 2015, the animal slaughtering and processing sector reported 26,600 nonfatal injuries and illnesses. The total recordable injury rate was 5.4 per 100 full-time workers, compared to 3.0 for private industry overall.
The most telling statistic involves injuries serious enough to require a job transfer or work restrictions but not necessarily time off. That rate was 2.7 per 100 workers, nearly four times the rate for private industry as a whole. Overexertion and repetitive motion injuries account for more than a third of the most serious cases. Workers also face exposure to ammonia and hydrogen sulfide gases from concentrated animal waste, along with biological hazards from handling live and slaughtered animals at high speed. Between 2011 and 2015, 73 workers were fatally injured in the industry.
Why Factory Farms Dominate
The economic math is straightforward. Confining large numbers of animals in a small space, automating feeding and waste systems, and using genetics optimized for rapid growth dramatically lowers the cost of producing each pound of meat, egg, or gallon of milk. Federal policy reinforces this model: the U.S. government spends up to $38 billion annually subsidizing the meat and dairy industries, with less than one percent of that going toward fruit and vegetable production.
Those subsidies flow disproportionately to the largest producers. Corn and soybeans, the two primary ingredients in livestock feed, are among the most heavily subsidized crops in the country. This keeps feed costs artificially low, which benefits operations buying millions of pounds of it each year far more than it helps a small diversified farm. The result is a system where the retail price of factory-farmed meat doesn’t reflect the environmental cleanup costs, public health burdens, or infrastructure damage associated with producing it.